Modeling coarse aggregate distribution in interfacial zone of new–old concrete in precast concrete structures

Abstract

There are a large number of interfacial zones of new-old concrete in precast concrete structures, and the wall effect causes the reduction of coarse aggregate in the interfacial zones, which leads to the weaker physical, mechanical and durability properties of this part. In the present paper, some new-old concrete specimens with different chiseled depths at the interfaces were made to simulate the wet joints of precast concrete structures. The distribution characteristics of the coarse aggregate volume fraction in the interfacial zones of new-old concrete specimens were obtained by DIP (Digital Image Processing) technology. The results show that the distribution of the coarse aggregate volume fraction in the interfacial zones is similar to a positive V-shape (no chiseling) or partial V-shape (chiseled interface), and is generally lower than that of the noumenons of new and old concrete (constant values). With the increase of chiseled depth, the valley point (i.e., the minimum value) of the distribution curve of coarse aggregate volume fraction in the interfacial zone will move upwards and offset toward the old concrete. When the offset reaches 2 mm from the interface, it remains stable. The multiple irregular cone-shape small pits on the actual chiseled surface are abstracted into a single bulging slope pit, and the area ratio of new-old concrete on the cross section within the chiseled range is derived. On this basis, the model of the coarse aggregate volume fraction in the interfacial zone varied with the distance from the interface is proposed.coarse aggregate distribution, interfacial zone, new-old concrete, precast concrete structure | INTRODUCTIONCompared with cast-in-place concrete structures, precast concrete structures have significant advantages in terms of production technology and environmental impact, so they have been widely used all over the world for decades. 1,2 With the extensive promotion of precast concrete structures in China in recent years, its application will be further expanded in the future. 3 Precast concrete structures have two connection modes: dry connection and wet connection, of which the latter is dominant. 4,5 In wet connection system, there are many seams between new and old concrete as well as a large number of steel bars connection nodes, which make the wet joints become the weak parts in physical, mechanical Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

Comparison of 2D and 3D meso‐model of concrete under high strain loading rate

“…The above-mentioned concrete parameters obtained with the meso-model differs from the macro model due do the consideration of aggregate, mortar, and ITZ as different phases. 8,9 Many researches have studied the effect of incorporation of aggregate and ITZ in the numerical model on the failure pattern and DIF of the concrete [10][11][12][13][14] under high strain loading rate. Zhou and Hao 8 studied and compared the 2D axisymmetric homogenous and meso-model and different results were obtained for both the models.…”

“…Many researches have studied the effect of incorporation of aggregate and ITZ in the numerical model on the failure pattern and DIF of the concrete 10–14 under high strain loading rate. Zhou and Hao 8 studied and compared the 2D axisymmetric homogenous and meso‐model and different results were obtained for both the models.…”